Method of inhibiting the acid corrosion of metals

ABSTRACT

WHERE: R=AN ALKYL, ALKENYL OR HYDROXYALKENYL RADICAL HAVING 5 TO 21 CARBON ATOMS M=0 OR INTEGER OF 1 TO 3   2-R,1-(NH2-(C2H4-NH)M-C2H4-)-2-IMIDAZOLINE   A METHOD OF PREVENTING THE ACID CORROSION OF METALS WHICH CONSISTS IN INHIBITING ACID SOLUTIONS FROM CORRODING METALS BY MIXING WITH SAID ACID SOLUTIONS AN ANTICORROSIVE COMPOSITION PREPARED BY THE REACTION OF BENZYL HALIDES AND MATERIALS MAINLY CONSISTING OF IMIDAZOLINE DERIVATIVES HAVING THE FOLLOWNG STRUCTURAL FORMULA

United States Patent O 3,736,098 METHOD OF lNI-IIBITING THE ACID CORROSION F METALS Toshiya Kataoka, Chigasaki-shi, and Atunobu Takada, Tokyo, Japan, assignors to Nisshin Oil Mills, Ltd., Tokyo, Japan N0 Drawing. Filed Jan. 18, 1972, Ser. No. 218,825 Int. Cl. C23f 11/14 US. Cl. 21-2.7 R 9 Claims ABSTRACT OF THE DISCLOSURE A method of preventing the acid corrosion of metals which consists in inhibiting acid solutions from corroding metals by mixing with said acid solutions an anticorrosive composition prepared by the reaction of benzyl halides and materials mainly consisting of imidazoline derivatives having the following structural formula:

where:

R=an alkyl, alkenyl or hydroxyalkenyl radical'havin'g 5 to 21 carbon atoms m=0 or integer of l to 3 BACKGROUND OF THE INVENTION This invention relates to a method of inhibiting metals from being corroded by acids and anticorrosive agents for metals.

It is generally known that compounds of the imidazoline series are effective to inhibit metals from being corroded by acids. Said effect primarily consists in inhibiting the surface of metals from being tarnished brown when they are in contact with, for example, a solution of hydrochloric acid.

Where l-(2'-aminoethyl)-2-alkyl (or alkenyl) imidazoline is used as an anticorrosive agent in subjecting metals to acid washing, said agent displays an effect of considerably preventing metals from being tarnished brown, in case the washing acid consists of hydrochloric acid. However, said anticorrosive agent is still deemed unsatisfactory to inhibit the corrosion weight loss of metals. Further, where there is used a hot washing acid solution over a long period, the anticorrosive agent contained therein presents a reduced elfeet due to its own hydrolysis, failing to be applied at all depending on the object of acid washing.

SUMMARY OF THE'INVEN'II-ON The present inventors have discovered that where 1-(2- aminoethyl)-2-alkyl (or alkenyl) imidazoline isreacted with benzyl halides to convert the valency of the nitrogen constituting an imidazoline ring to a tetravalent form; there-by obtaining imidazolinium salts, and the benzyl group is also introduced into the aminoethyl group, then the resultant composition has a far more excellent property of inhibiting metals from being corroded by an acid solution than the original 1-(2'-aminoethyl)-2-alky1 (or alkenyl) imidazoline alone.

This invention has been accomplished from the abovementioned discovery. According to one aspect of the invention, there is provided a method of inhibiting acid solutions from corroding metals by mixing said acid solu- 3,736,098 Patented May 29, 1973 tions with an anticorrosive composition prepared by the reaction of benzyl halides and materials mainly consistmg of imidazoline derivatives having the following structural formula:

R =group of alkyl, alkenyl or hydroxyalkenyl having 5 to 21 carbon atoms m=0 or integer of 1 to 3 According to another aspect of the invention, there is provided a method of inhibiting acid solutions from corroding metals by adding to said solutions not only an anticorrosive composition prepared by the reaction of benzyl halides and materials mainly consisting of imidazoline derivatives having the above-mentioned structural formula but also an additive capable of prominently promoting the solubility of said anticorrosive agent in acid solutions.

This invention far more reduces the weight loss of metals caused by acid corrosion than has been possible with the prior art, thereby fully protecting the metals from corrosion by hot acid solutions even when the metals are exposed thereto for long hours.

DETAILED DESCRIPTION OF THE INVENTION Imidazoline derivatives used as the raw material of the subject anticorrosive composition can be prepared 'by reacting fatty acids with polyethylene polyamines such as diethylene triamine (-DETA), triethylene tetramine (TETA), tetraethylene pentamine (TEPA) and pentaethylene hexamine (PEI-IA) by the ordinary process according to the following Equation 1:

RCOOH NH2(C2H4NH);C2H4NH1 r where R-=group of alkyl, alkenyl or hydroxyalkenyl x=integer of 1 to 4 m=0 or integer of 1 to 3.

olnlmnolnnm-nnoon [A] where: p=0 or integer of 1 or 2.

Since, however, the main component of said anticorrosive composition is substantially formed of a type represented by the structural formula shown in the reaction Formula 1, it is preferred for economic reason to use said composition in a state mixed with such byproducts expressed by the structural Formulas A and B instead of particularly separating them.

The anticorrosive composition of the Equation 1 may also be prepared by any desired process according to either of the following Equation 2 or 3.

Reaction of imidazoline derivatives with, for example, benzyl chloride included in the aforesaid benzyl halides easily proceeds by applying heat at a temperature of 60 to 150 C., or preferably 80 to 120 C.

The proportion of the benzyl halide which is to be reacted with the imidazoline derivatives should preferably be limited to such extent that the amount of said benzyl halide does not exceed an equivalent to the number of reactive imidazoline rings and amino groups contained in the molecule of the imidazoline derivatives, namely, that there do not remain large amounts of unreacted benzyl halide after completion of reaction.

Reaction of the imidazoline derivatives with the benzyl halide may be expressed by combinations of the following Equations 4 to 8, the resultant composition being formed of various mixtures of the reaction products.

Where X represents a halogen group as applied throughout the Equations 4 to 8.

-(n max Where n denotes 0 or an integer expressed by min The anticorrosive composition prepared by combinations of the above-mentioned reaction Formulas 4 to 8 includes an imidazolinium salt converted to a tetravalent form by the benzyl halide and an amino group mixed with a benzyl group and has a strong adsorptive capacity to the surface of metals. Further, the benzyl group, as well as the group of alkyl or alkenyl, prominently protects the surface of metals from acids. Therefore, addition of even extremely small amounts of the anticorrosive composition of this invention displays an excellent effect of protecting metals from acid corrosion.

The aforesaid composition of this invention has a prominent anticorrosive effect particularly against a solution of hydrochloric acid and is characterized in that when treated with a solution of hydrochloric acid containing small amounts of said anticorrosive composition, metals can maintain a surface free from undesirable smuts or brown tarnishes and as lustrous as that of original untreated metals, and present less weight loss by corrosion than when processed by a solution of hydrochloric acid containing only imidazoline derivatives which were not reacted with benzyl halides.

The anticorrosive composition of the invention has further advantage that while imidazoline derivatives before reacted with benzyl halides are easily subject to hydrolysis by a hot acid solution, the main component of the present anticorrosive composition consists of imidazolinium salts converted to a tetravalent form by being reacted with benzyl halides and consequently is little hydrolyzed even when mixed with a hot acid solution, retaining an anticorrosive eifect over a long period.

Referring to the alkyl or alkenyl group contained in the anticorrosive composition of this invention, the type having to 21 carbon atoms is eifective. Also effective is the alkenyl group containing a hydroxyl group derived from ricinoleic acid. This type of alkenyl group has a hydrophilic hydroxyl group positioned at the intermediate part of a carbon chain and consequently is characterized by rendering the anticorrosive composition less frothy.

When added to an acid solution, the anticorrosive composition of this invention which originally has low solubility therein naturally makes the solution turbid. Since, however, the composition is well dispersed, said turbidity itself does not normally exert a harmful effect on the anticorrosive effect of said composition, but enables it fully to protect metals from acid corrosion.

There are occasions, however, where an acid solution is not desired to be cloudy. In such case, the anticorrosive composition should be made sufiiciently soluble in said acid solution to maintain its transparency when mixed therewith. A solubilizer added to this end is required to be stable to an acid solution and free from a harmful efiect on the protection of metals from acid corrosion. Economically favorable are such solubilizers as ethylene oxide addition product of higher alcohols, alkyl phenols and alkyl amines. Where, therefore, the anticorrosive composition is used with a hot acid solution it is preferred that said composition be mixed with solubilizer for example, ethylene oxide addition product of alkyl amines which does not cause the acid solution to present a cloud oint. p The present invention will be more fully understood by reference to the examples which follow.

EXAMPLE 1 There were used the following types of anticorrosive composition.

(I) l- 2'-aminoethyl 2-cocoimidazoline (IA) A composition prepared by the reaction with 0.5 mol of benzyl chloride added based on 1.0 mol of the Type I (I-B) A composition prepared by the reaction with 1.0 mol of benzyl chloride added based on 1.0 mol of the Type I (I-C) A composition prepared by the reaction with 1.5 mol of benzyl chloride added based on 1.0 mol of the Type I (I-D) A composition prepared by the reaction with 2.0 mol of benzyl chloride added based on 1.0 mol of the Type I (I-E) A composition prepared by the reaction with 2.0 mol of benzyl iodide added based on 1.0 mol of the Type I (II) l-(2-aminoethyl)-2-rapeimidazoline (II-A) A composition prepared by the reaction with 2.0 mol of benzyl chloride added based on 1.0 mol of the Type II (III) 1-(2'-aminoethyl)-2-castorimidazoline (III-A) A composition prepared by the reaction with 2.0 mol of benzyl chloride added based on 1.0 mol of the Type IH (IV) 1-2-(2'-aminoethyl)aminoethyl-Z-undecyl imidazoline (IV-A) A composition prepared by the reaction with 2.0 mol of benzyl chloride added based on 1.0 mol of the Type IV (V) An imidazoline derivative prepared from lauric acid and TEPA V (V-A) A composition prepared by the reaction with 2.0 mol of benzyl chloride added based on 1.0 mol of theTypev a v(V-B).,A compositionprepared by .the. reaction with 3.0 mol of benzyl chloride added based on 1.0 mol of the Type V f (VI) An imidazoline derivative prepared from lauric acid and PEHA (VI-A) A composition prepared by-- the reaction with 3.0 mol of benzyl chloride added based on 1.0 mol of the Type VI (VI-B) A composition prepared by the reaction with 4.0 mol of benzyl chloride added based on 1.0 mol of the Type VI Among the above-listed corrosive compositions, those of the Types I, II, III, IV, V and VI only consist of imidazoline derivatives whichv were not reacted with benzyl halides. They were used simply as controls or reference samples in the tests of determining the capacity to prevent acid corrosion in order to distinguish more clearly the eifect of anticorrosive compositions of this invention. 7.

Cold pressed milled steel coupons (50 mm. x 20 mm. x 2 mm.) were submerged in 150 ml. of 7% hydrochloric acid solutions to which there were added prescribed amount of anticorrosive composition. The coupons were allowed to stand in said acid solutions for 5 hours at a temperature of 70 C. to measure their corrosion rates (mg./cm. /hr.). At the same time there were conducted blank tests with 7% pure hydrochloric acid solution. The percentage inhibition efficiency acid corrosion was determined by the following equation.

Percent inhibition eflieiency g X where The results of the corrosion inhibition tests are presented in Tables 1, 2 and 3 below.

TABLE 1.-CORROSION INHIBITING EFFECT [7% H01, 70 0., 5 hr.]

Anticorrosive composltion Inhibition eificieney,

percent 97. 7 Maintains the original metal luster. 99. 0 D0. 99. 1 Do.

99. 0 Do. 99. 4 Do. 99. 5 D0.

99. 2 Do. 99. 5 Do. 99. 6 D0.

99. 1 Do. 99. 5 D0. Do.

Do. Do.

Amount Corrosion added, rate, rng./ percent cmfi/hr.

Surface oi processed steel coupon Do. Presents a dark brown color due to occurrence of smuts.

TABLE 2.CORROSION INHIBITING EFFECT [7% H01, 70 C., 5 1m] Anticorrosive EXAMPLE 2 composition Amount Corrosion Inhibition 5 There were heated to 80 C. the 10% hydrochloric acid added, rate, mg./ efliciency, Suriace of processed Type Percent 99mm Steel COuPm solutions to which there were added a prescribed amount 0. 010 0.358 98.3 Maintains the original metallusten of the ant1corros1ve compositions of the Types I and 8:823 .8133; 32:? 3; 10 I-D used in Example 1. Said hydrochloric acid solutions 0,025 4 ,3 were preserved at said temperature for 5, 10 and 30 days 0. 050 0. 114 99. Do.

respectively. Thereafter, there were submersed, as in 0. 010 0. 514 97.5 Do. p 0.025 0. 305 98.3 D0. Example 1, mild steel coupons for 5 hours in sand 0.050 0.317 98.5 D0. d hl d 1 Th d d n 1 o tions. ere were n t 1 83g; 8 132 33 g by me o 0 ac s u co uc e corio '5 0. 0 (1050 @114 995 D0. SlOIl inhibition tests with said acid solutions kept at 70 Q 010 (1422 9&0 C. to determine the corrosion rate and inhibition elli- .3 D 8823 3 :3 33} 3 ciency and compare the high temperature stability of the 0.010 0.155 09.3 Do. respective samples, the results being presented in Table 0. 025 0. 120 99. 4 Do. 0.050 0.110 09.5 Do. 4 below.

0 20. 936 0 Presents a dark brown color due to occur- 95 rence of smuts.

TABLE 4.CORROSION INHIBITING EFFECT [10% EC], 70 0., 5 hr.]

Number of days during which HCl. remained mixed with anticorrosivc compositions (80 C.)

Anticorrosive composition 0 days 5 days 10 days days Amount Corrosion Inhibition Corrosion Inhibition Corrosion Inhibition Corrosion Inhibition added, rate, mg./ efficiency rate, mgJ efficiency, rate, n1g./ ctiiciency rate, mgJ eificiency, Type percent cmJ/hr. percent cm.'-/hr. percent cmfl/hr. percent crnF/hr. percent EXAMPLE 3 TABLE 3 CORROSION INHIBITING EFFECT There were submerged mild steel coupons in 150 mol 0 of the 10% sulfuric acid solutions to which there were (7% HCl, 70 c., 5 hit] added a prescnbed amount of the ant1corros1ve compos1- fig t i glzr r o gg tions of the Types I and I-E used in Example 1. The steel plate was allowed to stand 2 hours in said sulfuric Amount Corrosion Inhibition a added, rate, mg./ efficiency, Surface of processed Solution kept at a temperatllre of 60 Type percent wig/1m percent Steel coupon nation was made of the corrosion rate and mh1b1t1on V 0.010 0362 9&3 Maintains the Original efiic1ency, the results being presented in Table 5 below.

metal luster. v 0.025 0. 277 98. 7 Do. V 0. 050 0. 200 98. 8 Do.

B V A (1010 0.230 98.9 Do. TA LE 5 CORROSION PREVENTION EFFECT VA. 0. 025 0.170 00. 2 Do. [10% Insoi, 00 0., 21m] VA 0. 050 0. 168 00. 2 D05 Anticorroslve VB 0. 010 0. 237 98. 9 Do. composition V-B 0.025 0. 183 99. 1 Do. VB-... 0.050 0.172 99.2 Do. Amount Corrosion Inhibition added, rate,rng./ efficiency, Surface of processed steel VI 0.010 0. 400 07.7 D0. ype percent crnJ/lhr. percent coupon v1 0.025 0. 405 98.1 D0. v1 0,050 0402 93,1 D I 0.010 3. 45 75.0 Presented a dark brown color due to occurrence VI-A-.- 0. 010 0. 350 98. 3 D0. of smuts. VI-A--- 07 025 0. 200 as. 7 Do. I 0. 025 2. 71 80. 3 Do. VIAl. 0.050 0. 128 997 4 Do. I 0. 050 1. 91 86. 1 D0.

V1 B 0.010 1350 9g 3 D0 IE 0.010 0.27 98.0 Maintains the original VI-B... 0. 025 0. 232 98. 9 Do. metal luster. VH3..- 0. 050 0. 245 0s. 8 D0. 14? 025 0. 14 99. 0 Do. 0. 050 0. 07 00. 5 Do. 0 20. 936 0 Presents a dark brown 1 d to Occurence 0 13.77 0 Presents a dark brown of smuts.

color due to occurrence of smuts.

EXAMPLE 4 TABLE 7500912051010 INHIBITING urrao'r 7 H01, 70 G.,6hr.]

There were performed corrosion inhibition tests with A t' the anticorrosive compositions of the Types I, I-A, I-B, 031550550 So1 ubiv H'Ao IV A 5 m am tiii iii C rrosion t' i S f f 1011. 0 11! B108 0 Y1, VI-A and VI-B with the following types of solubiadded, ad d, rate,mg./ ciency, processed steel lizer added: yn percent percent cmJ/hr. percent coupon (A) Ethylene oxide addition product of lauryl alcohol II 0.010 0 5 9 Maiptains h having 25 mol of ethylene oxide per 1.0 mol of lauryl imesinal metal 11S er. alcohol. D 10 II 0.025 0 0.250 98.8 Do.

(B Ethylene oxide addition product of nonyl phe- 11 0 9 I 8.7 Do. n01 having 15 mol of ethylene oxide per 1.0 mol of nonyl II- 0.010 000.002 0.087 99. 0 Do. phenol. E 23 80 0% 0. 059 09. 0 Do.

(B Ethylene oxide addition product of nonyl phe- 2/ M86 I nol havin mol of eth l 1 0-010 0 (1514 97-5 Do.

h 1 g y ene oxide per 1 0 mol of nonyl 0' 025 0 (1365 983 Do. p eno 0. 050 0 0. 317 98.5 Do.

C Ethylene oxide addition product of stearylamine 0.010 Q1/0002 @105 99,5 having 15 mol of ethylene oxide per 1.0 mol of stearyl- 0.025 000.005 0111. Do. amine. III-A-.. 0. 050 000. 010 0. 115 99. 5 Do.

(C Ethylene oxide addition product of stearylamine 20 gj 8-8;? 3 3% 32-2 38- haying 20 mol of ethylene oxide per 1.0 mol of stearyl- IV- .I- 0. 050 0 0.313 9933 Do: amme- IVA- 0. 010 000. 002 0 141 00. 9 Do.

The results are presented in Tables 6, 7 and 8 below. g-fi-fl 8- 53 808-893 8-32 99.: Do. Through the tests there was used a transparent hydro- 2/ 0 20936 P d k resents 2. ar chloric acid solution free from turb1dity. 25 brown color due to occurrence of smuts.

TABLE 8.CORROSION INHIBITING EFFECT 7% H01. 70 0., 5 hr.]

TABLE 6.CORROSION INHIBITING EFFECT Anticonzz'sive s 1 b- H 1 0 com osi ion on 1- [7% lizer/ Inhibi- Amount amount Corrosion tion efii- Surface of Anticorrosive added, added, rate, mgJ ciency, processed steel composition Soil 1:25 Inhibi- Type percent percent cmfi/hr. percent coupon Amount amount Corrosion tion efli- Surface of V (L010 0 352 9&3 Maintains the added, added, rate, mg./ ciency, processed steel original metal Type percent percent emf/hr. percent coupon 25 0 277 98 7 luster. 0.0 0 Do. I- 0. 010 0 0. 484 97. 7 Maintains the 0 5 0 0 2 0 9g 8 original metal metal luster. 0. 010 Ci/O. 002 0. 107 99. 5 Do. I. 0. 025 0 0. 209 99. 0 D0. 0.025 000. 005 0. 111 99. 5 Do. I- 0. 050 0 0.185 99. 1 Do. 0. 050 000. 010 0.141 99. 3 Do. 0 010 000.002 0 190 991 Do. I 3 8%? :33; 3; 38:5 33; 0 025 000.025 0 155 90.3 Do. A/o 0170 0 050 (la/0.010 0 136 99.4 D0. 0 010 B00002 0 115 00.5 Do. M10 0 0 025 B00. 005 0 111 00.5 Do. @025 2 3- 0 050 B00. 010 0 110 90.5 Do. M50 0 0. 010 000. 002 0. 284 98.7 Do. 3 332 8 33; 0.025 000.005 0.205 90.5 D0. 0 Q50 C 0 0 0 0 996 Do. 0.050 (ll/0.010 0.103 99.5 D0. 0' 0. 010 000. 002 0. 300 98.5 D0; 8.852 550.8832 8.3% 33.? B3. 0025 000-005 0231 0 05 B2/() 0150 0 97 9 0.050 C2/0-010 0.167 99.2 D0. 0. 010 000.002 0.138 99.3 Do. 0 0 20-936 0 Presents 9 dark 0.025 000.002 0.100 00.5 Do. 0.050 000.010 0.095 99.5 D0. mm ofsmuts.

0 0 20. 936 0 Presents a dark grown color EXAMPLE 5 1305 0? gig ts. There were heated to 80 C. the 10% hydrochloric acid solutions to which there were added a prescribed amount TABLE 9.--00RROSION INHIBITION EFFECT [10% H01, 0., 5 hr.]

Number of days during which 1101 remained mixedwlth anticorrosive compositions C.)

0 days 5 days 10 days 30 days Anticorrosive composition Solubilizerl Amount amount Corrosion Inhibition Corrosion Inhibition Corrosion lnhihition Corrosion Inhibition added, added, rat efliciency, rate, efficiency, rate, eificiency, rate, efficiency percent percent mgJcmJ/hr. percent nigJcmfl/hr. percent mgJcmfl/hr. percent mgJcmfi/hr. percent of the anticorrosive compositions of the Types I and I-D used in Example 1 as well as the solubilizer of the type C;, used in Example 4. Said hydrochloric acid solutions were preserved at said temperature for 5, 10 and 30 days respectively. There were submerged, as in Example 1, a mild steel coupons for hours in said solutions. There were made corrosion inhibition tests with said solutions maintained at 70 C. to determine the corrosion rate and inhibition efficiency and compare the high temperature stability of the respective anticorrosive compositions. The results are shown in the foregoing Table 9.

What we claim is:

1. A method of inhibiting the acid corrosion of metals which consists of inhibiting acid solutions from corroding metals by mixing with said acid solutions an anticorrosive composition prepared by the reaction of benzyl halides and materials mainly consisting of imidazoline derivatives having the following structural formula:

where:

R=group of alkyl, alkenyl or hydroxyalkenyl having 5 to 21 carbon atoms m=0 or integer of 1 to 3 2. The method according to claim 1 wherein the benzyl halide is benzyl chloride.

3. The method according to claim 1 wherein the benzyl halide is benzyl iodide.

4. The method according to claim 2 wherein reaction of materials mainly consisting of imidazoline derivatives with the benzyl chloride is conducted at a temperature of 60 to 150 C.

5. A method of inhibiting the acid corrosion of metals which consists of inhibiting acid solutions from corroding metals by mixing with said acid solutions an anticorrosive composition prepared by the reaction of benzyl halides and materials mainly consisting of imidazoline derivatives having the following structural formula:

where:

R=group of alkyl, alkenyl or hydroxyalkenyl having 5 to 21 carbon atoms m=0 or integer of 1 to 3 and also mixing with said acid solution additives capable of rendering said anticorrosive composition soluble in said acid solutions.

6. The method according to claim 5 wherein the benzyl halide is benzyl chloride.

7. The method according to claim 5 wherein the benzyl halide is benzyl iodide.

8. The method according to claim 5 wherein the additives capable of rendering the anticorrosive composition soluble in acid solutions are selected from the group consisting of ethylene oxide addition products of higher alcohols, alkyl phenols and alkyl amines.

9. The method according to claim 5 wherein reaction of materials mainly consisting of imidazoline derivatives with the benzyl chloride is performed at a temperature Of to C.

References Cited UNITED STATES PATENTS 2,794,808 6/1957 Albrecht et a1 260309.6 3,096,294 7/1963 Hughes 260309.6 X 3,514,251 5/1970 Annand et a1 2l 2.7 R

MORRIS O. WOLK, Primary Examiner T. HAGAN, Assistant Examiner US. Cl. X.R. 

